What’s the Difference Between Ambient Light and On-Camera Flash?

What’s the Difference? is a series of video lighting tutorials. Each episode responds to a single question. In this episode, Jared Platt tries using on-camera flash to overpower the sun. The entire series, including all videos, articles and lighting diagrams, is available at our website. And feel free to leave a question to Jared in the comment section if you have one!

Some places in the world have a limited range of tones. Cloud cover and fog and even heavy smog tend to take the edge of the extremes. This makes capturing an image with a limited latitude much easier.

I have fantasies about living in such places. But then I also remember that I might have to wear a coat to stay warm. So I quickly dismiss the day dreams.

In times and places with limited contrast, a flash is used to add catch lights into the eyes, fill in subtle shadows or provide more volume with a stronger direction of light.

But in the harsh light of a dry, clear blue sky below (or above) the 40th parallel, you are going to experience the limits of your camera’s latitude regularly, and feel the challenge of lighting your shot just to balance the intensity of the light.

We took on this challenge by taking our bride and groom out into the city in the intense afternoon sun. During this challenge we compared a completely ambient shot to one using a simple on-camera flash set up.

With Ambient Light

Our first shot was taken without the assistance of a flash or a reflector. The camera was set to 1/60 sec at f 4.5, ISO 50.

We turned the couple away from the sun, so that their faces would be lit by the soft light of the north-earstern sky, while the direct sun acted as our hairlight.

With the image properly exposed for their faces, the couple is well lit. This could pass for a nice portrait.

But it could be much better.

With On-Camera Flash

In order to bring in the beautiful blue sky we needed to lower the ambient exposure by more than two stops (1/200 sec at f 6.3 at ISO 50). But if we continued to shoot without the assistance of a flash, our couple would be extremely dark, in silhouette even. A flash needed to be added.

Of course, adding an off-camera flash would be ideal. But sometimes you just don’t have the luxury of an assistant or even a stand. So we wanted to see what this shot would look like with an on-camera flash.

The resulting image shows a beautiful blue sky (thanks to our ambient settings) and a well lit couple (thanks to our on-camera flash).

Note that on-camera flash can be dangerously obvious. It can also flatten out your subject. So it is important to be as subtle as possible.

When I’m operating in TTL Mode with an on-camera flash, I will typically dial down the flash compensation by 2/3 of a stop. By doing this, the flash is not allowed to completely overpower the ambient light. In this case you can see that there is still a lot of shape to their cheek bones and to his forehead. This is all a result of limiting the power of the on-camera flash.

Conclusion

It’s my preference to always have my flash off camera. But there are times when an on-camera flash is the only viable way to accomplish the task.

Either way, knowing when to turn the flash on and how to keep the on-camera fill light subtle is the key to dramatic portraits on-the-go, complete with those deep blue skies.